1. Field of the Invention
The present invention relates to a quick-change holder for a machine tool, in which an adaptor holding a tool is attached to and detached from a body fixed to the spindle of the machine tool, and more particularly to a quick-change holder of such single-action type as can have its nut attached and detached easily by one hand.
2. Description of the Prior Art
A quick-change holder according to the prior art is made to have such a construction as is shown in FIG. 1 (PRIOR ART). As shown, a nut loaded with a tool can be attached to and detached from a holder body by the radial movements of a plurality of balls which are mounted in radial through holes formed in the body.
When the aforementioned adaptor is removed, however, the condition is shown in FIG. 2, in which the balls restore their initial positions shown in FIG. 1 and are blocked by the smaller diameter portion of the inner circumference of the sleeve being urged by the action of a spring so that they cannot move outwardly in the radial direction. Therefore, the nut cannot be inserted into the holder body before the sleeve is moved leftwardly against the action of the spring so that the balls are set free and escaped onto the larger diameter portion of the inner circumference of the sleeve.